Prevent kevent(2) use of EVFILT_EXCEPT with FIFOs and pipes

Currently, the only intended direct usage of the EVFILT_EXCEPT filter
is with NOTE_OOB to detect out-of-band data in ptys and sockets.
NOTE_OOB does not apply to FIFOs or pipes. Prevent the user from
registering the filter with these file types. The filter code is for
the kernel's internal use.

OK mpi@

diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index 4da474a..fa103c6 100644 (file)
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sys_pipe.c,v 1.131 2021/12/08 13:03:52 visa Exp $     */
+/*     $OpenBSD: sys_pipe.c,v 1.132 2021/12/13 14:54:22 visa Exp $     */
 
 /*
  * Copyright (c) 1996 John S. Dyson
@@ -927,6 +927,11 @@ pipe_kqfilter(struct file *fp, struct knote *kn)
                        error = EPERM;
                        break;
                }
+               if ((kn->kn_flags & __EV_POLL) == 0) {
+                       /* Disallow usage through kevent(2). */
+                       error = EINVAL;
+                       break;
+               }
                kn->kn_fop = &pipe_efiltops;
                kn->kn_hook = rpipe;
                klist_insert_locked(&rpipe->pipe_sel.si_note, kn);

diff --git a/sys/miscfs/fifofs/fifo_vnops.c b/sys/miscfs/fifofs/fifo_vnops.c
index f40e295..86b4486 100644 (file)
--- a/sys/miscfs/fifofs/fifo_vnops.c
+++ b/sys/miscfs/fifofs/fifo_vnops.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: fifo_vnops.c,v 1.87 2021/12/11 09:28:26 visa Exp $    */
+/*     $OpenBSD: fifo_vnops.c,v 1.88 2021/12/13 14:54:22 visa Exp $    */
 /*     $NetBSD: fifo_vnops.c,v 1.18 1996/03/16 23:52:42 christos Exp $ */
 
 /*
@@ -544,6 +544,10 @@ fifo_kqfilter(void *v)
                        /* Prevent triggering exceptfds. */
                        return (EPERM);
                }
+               if ((ap->a_kn->kn_flags & __EV_POLL) == 0) {
+                       /* Disallow usage through kevent(2). */
+                       return (EINVAL);
+               }
                ap->a_kn->kn_fop = &fifoexcept_filtops;
                so = fip->fi_readsock;
                sb = &so->so_rcv;